The present invention relates to phased array sensor systems and more specifically to a signal processing system, which operates in parallel with the outputs of sensors of an adaptive array, for quickly nulling multiple jammers.
Basically adaptive antenna arrays are utilized to receive desired information signals in a predetermined frequency band while at the same time rejecting undesired interference signals in the same frequency band. To accomplish this, the information signals and inteference signals must be received from the different directions. In one typical operating environment, the antenna array is physically mounted in a guided missile; and the information signals are transmitted by the missile controller from one direction while the interference signals are intentionally transmitted by an alien source from another direction. Such interference signals are commonly known as jamming signals.
In the art, various adaptive antenna arrays have been disclosed which attempt to overcome the above described problem. These prior art arrays include LMS (least means squares) arrays, MSN (maximum signal to noise ratio) arrays, SMI (simple matrix inversion) arrays, and RS (random search) arrays. All of these arrays, and the algorithms upon which their performance is based, have been well described in the literature and, with the exception of the least means squares systems, they will not be further described herein.
Additionally, the task of eliminating jamming signals is alleviated by the prior art techniques given by the following patents: U.S. Pat. Nos. 4,079,379 issued on Mar. 14, 1978 to Piesinger; 4,173,759 issued on Nov. 6, 1979 to Bakhru; and 4,217,586 issued on Aug. 12, 1980 to McGuffin.
However none of the above references disclose a system for nulling multiple jammers which operates in parallel with each antenna of an adaptive array. Therefore while the references are improvements over the traditional LMS system (the Bakru device can suppress a single jamming signal in less than 100 microseconds) all of the above references should, like prior systems using the LMS algorithm, exhibit slow rates of adaptation when interfering sources of widely different strengths are present. The present invention overcomes this slow convergence by employing a signal processing operation in parallel with the array combiner.